GNOME Calendar nightly (version 52) now reacts in real time, across all its views, when you change the first day of the week in GNOME Settings: https://gitlab.gnome.org/GNOME/gnome-calendar/-/work_items/1525
This is the kind of user experience I aim for. Thanks to all who made this integrated desktop UX possible: @jamie (GNOME settings schema), Alen (gnome-control-center UI), @GeopJr (GNOME Shell), yours truly (GNOME Calendar part 1) and Alen (GNOME Calendar part 2: Dynamic Edition)!